He paused to examine a long coil of hangman's rope and to read, smirking, the card propped on a magnificent necklace of opals, Caution: Do Not Touch. Cursed—Has Claimed the Lives of Nineteen Muggle Owners to Date.
A noise not unlike thunder broke out from somewhere overhead at this point, as Giant Wimbleweather burst into one of those not very intelligent laughs to which the nicer sorts of Giant are so liable.
Harry and Hermione went to see. Malfoy, Crabbe, and Goyle were standing in the shadow of a tree below. Crabbe and Goyle seemed to be keeping a lookout; both were smirking.
But just keep in mind that smirking is sometimes used when you notice that somebody has gotten something wrong, or you have something up on somebody else.